FIG. 4 shows a cross-sectional view of a prior art photodetector device disclosed in Japanese Published Patent Application 63-43366. In FIG. 4, reference numeral 1 designates a CdTe substrate. Light absorption layers 4 are disposed on the CdTe substrate 1. A p type CdHgTe layer 2 is disposed on the CdTe substrate 1 covering the light absorption layers 4. N type CdHgTe regions 3a and 3b are disposed in the surface of the p type CdHgTe layer 2.
This photodetector device will operate as follows.
First of all, the crosstalk which is a problem in a rear surface incident type photodetector device having an array type light receiving section will be described. FIG. 5 shows a device in which the light absorption layers 4 are removed from the photodetector device of FIG. 4.
First of all, the infrared rays which are incident on the rear surface of the CdTe substrate 1 are absorbed by the p type CdHgTe layer 2, thereby generating charge carriers 5. When these carriers 5 reach the pn junctions at the neighborhood of the n type CdHgTe regions 3a and 3b, a photocurrent is generated, thereby enabling detection of infrared light. However, when the picture elements are arranged at higher density, the diffusion distance of carriers 5 becomes longer relative to the separation of the picture elements, and the carriers 5 generated by incident light may reach any of picture elements of the n type CdHgTe regions 3a and 3b, as shown in FIG. 5, thereby resulting in crosstalk. In the prior art device, since the light absorption layers 4 prevent light incidence between picture elements, carriers are not generated between picture elements.
When the density of picture elements is increased in the prior art photodetector device, the carriers 5 generated in the neighborhood of the picture element of the n type CdHgTe region 3a diffuse to the picture element 3b regardless of whether the light absorption layers 4 are provided, thereby producing crosstalk and lowering the resolution of the picture element.